Silent chain

ABSTRACT

Provided is a silent chain that enables adjustment of the stiffness and balance of stiffness between upper and lower sides of guide plates, and that prevents long pin failure resulting from deflection or torsional deformation while securing a sufficient area and strength for the portion contacting a side face of a sprocket. The guide plate has a lightening hole with an upper end positioned above a pitch line, and a lower end extending out beyond lines that connect intersections between inner side edges of front and rear pin fitting holes and the pitch line, and a midpoint of a lower end edge of the guide plate in a front to back direction. Outermost portions of the lightening hole in a longitudinal direction are formed within a range that does not go beyond a pair of vertical lines vertical to the pitch line passing through the intersections.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a silent chain in which guide rows ofguide plates and middle plates, and non-guide rows of inner plates arealternately connected along a chain longitudinal direction by pairs ofrocker pins each formed of a long pin and a short pin. The presentinvention also relates to guide plates of the silent chain.

2. Description of the Related Art

A silent chain 500, in which guide rows 501 of a pair of left and rightguide plates 510 and middle plates 520, and non-guide rows 502 of aplurality of inner plates 530 are alternately connected along the chainlongitudinal direction by pairs of rocker pins 504 each formed of a longpin 540 and a short pin 550 as shown in FIGS. 3 to 5, has conventionallybeen known.

The long pins 540 are securely fitted in pin holes 511 of the guideplates 510 and seated in pin holes of the middle plates 520 and do notrotate relative to the pin holes.

The short pins 550 are seated in pin holes 531 of the inner plates 530and do not rotate relative to the pin holes.

Thus the long pin 540 and short pin 550 rolling in direct contact witheach other allow the chain to flex at the joint between the guide row501 and the non-guide row 502.

When the silent chain 500 is straight, as shown in FIG. 4, the rollingsurface of the long pin 540 and the rolling surface of the short pin 550are in contact with each other on a pitch line, and the pins can rollboth upward and downward.

Since the stiffness against tensile load is different between toothedmiddle plates 520 and toothless guide plates 510, when such a silentchain 500 is subjected to tension in the chain pitch direction, the lessstiff middle plates 520 elongate more in the chain pitch direction thanthe more stiff guide plates 510, which causes the long pin 540 to warpand sometimes to break.

In order to make the elongation in the guide plates 510 and middleplates 520 equal, for example, the guide plates 510 are provided withlightening holes 512 as shown in FIGS. 3 and 5 so as to reduce thestiffness against tensile load (tensile stiffness) of the guide plates510 to be equal to the tensile stiffness of the middle plates 520.

Guide plates shown in FIGS. 7 and 8 of Japanese Patent ApplicationLaid-open No. H11-236950 are also known as another design forconventional silent chains that use long pins and short pins.

SUMMARY OF THE INVENTION

If the lightening hole is simply enlarged to reduce the stiffness, theguide plate cannot have a sufficient area or strength of a portion thatmakes contact with a side face of the sprocket. While the stiffness inthe chain pitch direction of the known guide plate is made equal to thatof the middle plate by limiting the hole to a certain size, a goodbalance of stiffness in the height direction against tension on thepitch line is not taken into consideration. Thus there was a problemthat elongation on the pitch line differed from that of the middleplate.

Since the teeth of the middle plates meshing with the sprocket are notpositioned on the pitch line, the middle plates are subjected to a forcein a direction in which the front and rear teeth are spread apart, whichcauses deflection or torsional deformation of the long pins. Suchdeformation is not taken into consideration for the know guide plate.

In high load power transmission applications, in particular, deflectionor torsional deformation of the long pins led to vibration ormeandering, if not failure, and such vibration or meandering could notbe sufficiently suppressed.

The present invention has been contrived to solve these problems, andthe object thereof is to provide a silent chain that has a simple shape,that enables adjustment of the stiffness and balance of stiffnessbetween upper and lower sides of guide plates, and that prevents longpin failure resulting from deflection or torsional deformation andsuppresses vibration and meandering while securing a sufficient area andstrength for the portion contacting a side face of a sprocket.

The silent chain according to the present invention includes: guide rowsof guide plates and middle plates; and non-guide rows of inner plates,the guide rows and non-guide rows being alternately connected along achain longitudinal direction by pairs of rocker pins each formed of along pin and a short pin. The above object is achieved by the followingfeatures: The guide plates each include a pair of front and rear pinfitting holes in which the long pins are fitted, and a lightening holeformed in a middle portion between the front and rear pin fitting holes.The lightening hole is formed such that an upper end thereof ispositioned above a pitch line. The lightening hole is formed such that alower end thereof extends out beyond lines that connect intersectionsbetween inner side edges of the front and rear pin fitting holes and thepitch line, and a midpoint of a lower end edge of the guide plate in afront to back direction. Outermost portions of the lightening hole in alongitudinal direction are formed within a range that does not go beyonda pair of vertical lines vertical to the pitch line passing through theintersections.

With the silent chain according to claim 1 and the guide plate accordingto claim 4, the upper end of the lightening hole is positioned above thepitch line, and the lower end of the lightening hole extends out beyondlines that connect intersections between inner side edges of the frontand rear pin fitting holes and the pitch line, and a midpoint of thelower end edge of the guide plate in a front to back direction.Therefore, the balance of stiffness in the height direction of the guideplate against tension on the pitch line can be made equal to that ofmiddle plates so as to make the elongation on the pitch line equal tothat of the middle plates. Also, the stiffness in the same direction asthe direction of deformation of middle plates meshing with a sprocketcan be reduced, so as to prevent failure resulting from deflection ortorsional deformation of the long pins and to sufficiently suppressvibration and meandering.

Since the outermost portions of the lightening hole in a longitudinaldirection are formed within a range that does not go beyond a pair ofvertical lines vertical to the pitch line passing through theintersections, the guide plate can have a sufficient area and strengthin the portion contacting a side face of the sprocket.

According to the configuration set forth in claim 2, the upper end ofthe lightening hole is formed within a range that does not go beyondlines that connect the intersections between the inner side edges of thefront and rear pin fitting holes and the pitch line, and a midpoint ofan upper end edge of the guide plate in a front to back direction. Thusbending stiffness above the pitch line can be increased and deformationcan be made equal to that of the middle plate meshing with the sprocket.

According to the configuration set forth in claim 3, the lightening holeis formed in a rectangular shape, an upper side and a lower side of thelightening hole are parallel to an upper end edge and the lower end edgeof the guide plate, respectively, and corners of the lightening hole arerounded. With the lightening hole having such a simple shape, productionis made easy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustrative diagram of a silent chain according to oneembodiment of the present invention:

FIG. 2 is a side view of a guide plate of the silent chain according toone embodiment of the present invention;

FIG. 3 is an illustrative diagram of a conventional silent chain;

FIG. 4 is a partial cross-sectional view of the conventional silentchain; and

FIG. 5 is a side view of a guide plate of the conventional silent chain.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention is a silent chain in which guide rows of guideplates and middle plates, and non-guide rows of inner plates arealternately connected along a chain longitudinal direction by pairs ofrocker pins each formed of a long pin and a short pin. The guide plateseach include a pair of front and rear pin fitting holes in which thelong pins are fitted, and a lightening hole formed in a middle portionbetween the front and rear pin fitting holes. The lightening hole isformed such that an upper end thereof is positioned above a pitch line.The lightening hole is formed such that a lower end thereof extends outbeyond lines that connect intersections between inner side edges of thefront and rear pin fitting holes and the pitch line, and a midpoint of alower end edge of the guide plate in a front to back direction.Outermost portions of the lightening hole in a longitudinal directionare formed within a range that does not go beyond a pair of verticallines vertical to the pitch line passing through the intersections. Inspecific embodiments, the invention may be carried out in any form.

Various constituent elements of the silent chain of the presentinvention can be made of any materials as long as they have strength formaintaining appropriate tension of the chain. From the viewpoints ofstrength, machinability, and economy, iron-based materials such assteel, cast iron and the like are preferable. Guide plates, middleplates, and inner plates, in particular, should preferably be formed bypunching from a steel sheet.

A silent chain that is one embodiment of the present invention will behereinafter described with reference to the drawings.

Embodiment 1

The silent chain 100 that is one embodiment of the present invention issimilar to the conventional silent chain 500 shown in FIGS. 3 and 4except for lightening holes 112 in guide plates 110 as shown in FIG. 1.(Reference numerals given to the elements corresponding to those ofFIGS. 3 and 4 begin with 1.)

The guide plate 110 includes pin fitting holes 111 in which long pins140 are securely fitted, and a lightening hole 112 formed in a middlepart between the front and rear pin fitting holes 111 as shown in FIG.2.

In this embodiment, the lightening hole 112 is rectangular. The upperand lower sides of the lightening hole 112 are parallel to the upper endedge and lower end edge of the guide plate 110, respectively. Thecorners of the lightening hole 112 are rounded.

The lightening hole 112 is formed such that its upper side is locatedabove the pitch line P.

Both ends of the lower side of the lightening hole 112 extend as far asto the outside of lines that connect intersections T between inner sideedges of the front and rear pin fitting holes 111 and the pitch line P,and a midpoint C1 in the front to back direction of the lower end edgeof the guide plate 110.

Both ends of the lightening hole 112 in the longitudinal direction areformed within a range that does not go beyond a pair of vertical lines Vvertical to the pitch line passing through the intersections T.

In this embodiment, both ends of the upper side of the lightening hole212 are formed within a range that does not go beyond the lines thatconnect intersections T between inner side edges of the front and rearpin fitting holes 111 and the pitch line P, and a midpoint C2 in thefront to back direction of the upper end edge of the guide plate 110.

In the guide plate 110 thus formed, connected portions above and belowthe lightening hole 112 are present on upper and lower sides of thepitch line P. Therefore, when reducing the stiffness against tension onthe pitch line P, the balance of stiffness in the height direction ofthe guide plate 110 can be readily made equal to that of the middleplate 120 only by adjusting the heights of the upper and lower connectedportions, so that elongation on the pitch line P can be made equal tothat of the middle plate 120.

Since both ends of the lower side of the lightening hole 112 extend asfar as to the outside of lines that connect intersections T betweeninner side edges of the front and rear pin fitting holes 111 and thepitch line P, and a midpoint C1 in the front to back direction of thelower end edge of the guide plate 110, the bending stiffness of theconnected portion below the lightening hole 112 against a force thatacts in a twisting direction of the long pin 140 can be reduced. Thustwisting deformation of the long pin 140 caused by a force in adirection in which the teeth of the middle plate 120 are spread apart inthe front to back direction as the plate meshes with the sprocket can bemitigated.

Since both ends of the lower side of the lightening hole 112 extend asfar as to the outside of lines that connect intersections T betweeninner side edges of the front and rear pin fitting holes 111 and thepitch line P, and a midpoint C1 in the front to back direction of thelower end edge of the guide plate 110, the bending stiffness of thelower connected portion can be reduced. This enables the guide plate 110to have a sufficient area and strength in a portion that makes contactwith a side face of the sprocket, since there is no need to make thinnerthe lower connected portion to reduce the stiffness against tension onthe pitch line P.

While the lightening hole 112 is rectangular in which corners arerounded in this embodiment, the hole may be trapezoidal, triangular, orpolygonal, and each or all of the sides may be formed as curved lines.

What is claimed is:
 1. A silent chain comprising: guide rows of guideplates and middle plates; and non-guide rows of inner plates, the guiderows and non-guide rows being alternately connected along a chainlongitudinal direction by pairs of rocker pins each formed of a long pinand a short pin, the guide plates each including a pair of front andrear pin fitting holes in which the long pins are fitted, and alightening hole formed in a middle portion between the front and rearpin fitting holes, the lightening hole being formed such that an upperend thereof is positioned above a pitch line, the lightening hole beingformed such that a lower end thereof extends out beyond lines thatconnect intersections between inner side edges of the front and rear pinfitting holes and the pitch line, and a midpoint of a lower end edge ofthe guide plate in a front to back direction, outermost portions of thelightening hole in a longitudinal direction being formed within a rangethat does not go beyond a pair of vertical lines vertical to the pitchline passing through the intersections.
 2. The silent chain according toclaim 1, wherein the upper end of the lightening hole is formed within arange that does not go beyond lines that connect the intersectionsbetween the inner side edges of the front and rear pin fitting holes andthe pitch line, and a midpoint of an upper end edge of the guide platein a front to back direction.
 3. The silent chain according to claim 1,wherein the lightening hole is formed in a rectangular shape, an upperside and a lower side of the lightening hole are parallel to an upperend edge and the lower end edge of the guide plate, respectively, andcorners of the lightening hole are rounded.
 4. A guide plate used in asilent chain including guide rows and non-guide rows alternatelyconnected along a chain longitudinal direction by pairs of rocker pinseach formed of a long pin and a short pin, the guide plate comprising: apair of front and rear pin fitting holes in which the long pins arefitted; and a lightening hole open in a middle portion between the frontand rear pin fitting holes, the lightening hole being formed such thatan upper end thereof is positioned above a pitch line, the lighteninghole being formed such that a lower end thereof extends out beyond linesthat connect intersections between inner side edges of the front andrear pin fitting holes and the pitch line, and a midpoint of a lower endedge of the guide plate in a front to back direction, outermost portionsof the lightening hole in a longitudinal direction being formed within arange that does not go beyond a pair of vertical lines vertical to thepitch line passing through the intersections.